The scope of this project is to describe the molecular events involved in the neuronal induction and maintenance of serotonin-N-acetyltransferase (NAT) in the rat pineal gland. Present investigations showed that partial inhibition of RNA synthesis could not be correlated with inhibition of the induced rise in NAT. In most cases the inhibition of RNA synthesis was at lease two-fold greater than inhibition of NAT induction. Ornithine decarboxylase was also examined in rat pineals under conditions leading to NAT induction. No change in decarboxylase activity was observed. This supports a lack of involvement of new r-RNA synthesis in the induction process since the decarboxylase has been hypothesized to regulate RNA polymerase I which synthesizes r-RNA. 3'-5'-cAMP has been implicated in the maintenance of elevated levels of NAT in vivo. Presently we are attempting to derive in vitro conditions which mimick the in vivo situation.